(1) Field of the Invention
The present invention relates to a vehicular AC generator having a salient-pole-rotating stator supported by brackets.
(2) Description of the Related Art
A conventional general vehicular AC generator will be described with reference to FIG. 1 to FIG. 4. In the figures, a reference numeral 1 represents rear brackets of the generator each having an inlet opening 1a and an outlet opening 1b. A reference numeral 2 represents a rectifier, 3 is a brush holder having a regulator 3a, and 4 is a rotor consisting of a pair of cores 4a1 and 4a2 and is supported and fixed to a rotating shaft 5. A reference symbol 4b designates a plurality of trapezoidal-shaped claws functioning as magnetic poles periodically protruding from the edges of the outer peripheries of the cores 4a1 and 4a2. The claws 4b of the core 4a1 and the claws 4b of the core 4a2 are alternately arranged in such a way that each of the claws belonging to one of the pair of cores is arranged in a concave portion between adjacent two of the claws belonging to the other one of the pair of cores. A reference numeral 6 is a coil field accommodated within both of the cores 4a1 and 4a2. Reference symbols 7a and 7b designate centrifugal fans respectively attached to the side surfaces of the cores 4a1 and 4a2. Reference numeral 8 represents a stator arranged on the outer periphery of the rotor 4, and consisting of a core 8a and coil ends 8b and 8c. Reference numeral 9 is a front bracket having an inlet opening 9a for sucking outside air and an outlet opening 9b for exhausting air. Reference numerals 10a and 10b represent bearings for supporting the rotating shaft 5.
Next, in the vehicular AC generator constructed as above, a cooling channel will be described. First, outside air is sucked from the rear bracket 1 through the inlet opening 1a to cool the rectifier 2 and the regulator 3a. Then, the cooling air is strongly sucked by the centrifugal fans 7a to be bent so as to cool the coil end 8b of the rear side of the stator 8, and is exhausted from the outlet opening 1b. On the other hand, outside air from the front bracket 9 is flown through the inlet opening 9a and is separated to be flown into two channels, i.e., on one hand, is sucked by the centrifugal fans 7b to be bent so as to cool the coil end 8b of the front side of the stator 8 and is exhausted from the outlet opening 1b, and on the other hand, to cool the coil field 6 and then is flown to the rear side and is exhausted from the outlet opening 1b. 
In such a general type of the conventional vehicular AC generator, since the gap between the outer periphery surface of the shoulder portion of each of the claws 4b and the coil end 8b or 8c is small, and since the inner surfaces of the coil ends 8b and 8c are irregular, there is a problem in that ragged sound caused by cutting wind (interfering sound between the coils 4a1 and 4a2 and the coil ends 8b and 8c) is generated.
A prior art AC generator to solve such a problem is disclosed in, for example, Japanese Laid Open Patent Application (Kokai) No. 1-74163/89. This prior art AC generator will be described with reference to FIG. 5.
FIG. 5, the same parts as those in the above-described conventional general AC generator are denoted by the same reference symbols, and the explanation thereof are omitted here. Reference numeral 11 designate tapered portions of the outer periphery surfaces of the shoulders of the claws 4b each having a sloping surface against the end surface in the shaft direction.
By forming the tapered portions 11 in the claws 4b as above, the gap between each tapered portion 11 of the outer periphery surface of the claw 4b and each of the coil ends 8b and 8c is gradually increased in the direction toward the end surface, resulting in that the interference sound generated, during the rotation of the cores 4a1 and 4a2, between each of the cores 4a1 and 4a2 and each of the coil ends 8b and 8c is reduced.
In the prior art vehicular AC generator shown in FIG. 5, although the interference noise between each of the cores 4a1 and 4a2 and each of the coil ends 8b and 8c can be reduced by the tapered portions 11 in the outer periphery surfaces of the claws 4b, however, the gap between each of the centrifugal fans 7a and 7b and each of the coil ends 8b and 8c is still kept to be narrow in order to ensure a cooling efficiency of the coil ends 8b and 8c. Because the gap between each of the centrifugal fans 7a and 7b and each of the coil ends 8b and 8c is so narrow, there is a problem in that noise sound caused by cutting wind is generated between each of the coil ends 8b and 8c and each of the centrifugal fans 7a and 7b during the rotation of the centrifugal fans 7a and 7b. 
An object of the present invention is to resolve the above-mentioned problems, and to provide a vehicular AC generator in which noise sound caused by cutting wind by the rotation of centrifugal fans can be reduced.
Another object of the present invention is to provide a vehicular AC generator in which the cooling efficiency of coil ends of a stator by means of the centrifugal fans is not lowered even when the outer diameters of the centrifugal fans are made small.
Still another object of the present invention is to provide a vehicular AC generator in which noise sound caused by cutting wind by cores can be reduced by making the lowering of the output current due to the decrease of the outer diameters of centrifugal fans to be smaller.
According to the first aspect of the present invention, there is provided, for achieving the above object, a vehicular AC generator in which at least one of a pair of front and rear fans attached to the both ends of a core of a rotor has a outer diameter in the range between 85% and 96% of an outer diameter of the core.
According to the second aspect of the present invention, there is provided a vehicular AC generator having a side plate fixed to the end portion of one of the fans and having an outer diameter smaller than the outer diameter of the fan.
According to the third aspect of the present invention, there is provided a vehicular AC generator in which each of the tapered portions formed in the claws is provided in at least the front side of the direction of rotation in the width of the circumferential direction of each claw.
As stated above, according to the first aspect of the present invention, since the diameter of the fan is made to be in the range between 85% and 96% of the outer diameter of the core, noise caused by the fans themselves can be reduced, and the sound caused by cutting wind generated between the fans and the coil ends during the rotation of the fans can be reduced.
Further, according to the second aspect of the present invention, since the side plate is attached to the fan, the reduction of the amount of the cooling wind due to the decrease of the outer diameter of the fan can be prevented.
Still further, according to the third aspect of the present invention, since each of the tapered portions is provided in at least the front side of the direction of rotation in the width of the circumferential direction of each claw, the lowering of the output current due to the decrease of the outer diameter of the rotor core can be prevented.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.